The isolation of biologically important peptides from the thymus gland has been studied extensively in the last few years. Several peptides have been shown to play certain roles in T-cell maturation. Thymosin .alpha..sub.1, a highly acidic acetyl octacosapeptide isolated from calf thymus gland and characterized by sequence analysis has been reported to exhibit biological activities involved in the development of thymus-dependent lymphocytes (T-cells). Desacetyl thymosin .alpha..sub.1 has been reported to exhibit the same biological activity as thymosin .alpha..sub.1 and further can act as an intermediate in the preparation of thymosin .alpha..sub.1.
The isolation and characterization of thymosin .alpha..sub.1 was disclosed in U.S. Pat. No. 4,079,127. Synthesis of this peptide by solution and solid phase procedures was disclosed in U.S. Pat. No. 4,148,788.
An alternate solution phase synthesis for thymosin .alpha..sub.1 employing a different synthetic strategy was described by Birr and Stollenwerk, Angew. Chem.Int.Ed.Engl. 18, 394 (1979).
A solid phase synthesis of desacetyl thymosin .alpha..sub.1 was described by Merrifield et al. at the Fifteenth European Peptide Symposium (Poland) in September, 1978 and was published in the Proceedings of the Fifteenth European Peptide Symposium published June 1979. It was also described by Merrifield in the Alan E. Pierce Award Lecture on Solid Phase synthesis at the 6th American Peptide Symposium given June 20, 1979 and published December, 1979. See also these authors Biochem. 19, 3233 (1980).
In addition, the biosynthesis of desacetyl thymosin .alpha..sub.1 by a recombinant microorganism constructed by use of recombinant DNA technology has been described by Crea and Wetzel, U.S. patent application Ser. No. 125,685, filed Feb. 28, 1980.